Torchlight II - GUTS Editor Available

GUTS is our in-house development tool. It lets you modify almost everything about Torchlight II, from item and skill balance, to level layouts, animations, quests, and much more. GUTS mods can be shared with your friends, and multiplayer games using mods can be found in the modded games lobby. In addition, A new launcher lets you customize which mods are currently active.
When playing modded games, you can view your mod history, any previously played mods, and the impact disabling mods may have on your character.
We've also added a special tool to GUTS designed to convert pre-GUTS mods into the official mod format, with an eye toward making the transition much easier for our ambitious early modders.
We've tried to make the process as seamless as possible, with a focus on allowing modded multiplayer games with a minimum of fuss.

They also have a Q&A with their tools engineer Greg Brown, art director Jason Beck and lead level designer Patrick Blank.

Tell us about GUTS! Does it stand for anything? How did that name come about? GUTS is the new version of our content editor we used to create all the content for Torchlight II. We use it to make most things in the game - Levels, skills, classes, monsters, items, spawn classes, balance curves, UI, etc. Pretty much the only things we don't use it for are model, animation, 2D art/texture, and music/sound creation. We use 3D Studio Max, Photoshop, and whatever Matt uses down in California for those. We started this project with "TorchED" which was used for Torchlight, but we've made a large number of improvements and additions for GUTS.GUTS doesn't really stand for anything. The dry and boring story is that we compile the game source as a DLL for the editor which was originally called "core.dll" but that was confusing because we had another class called "core" so I changed the name to "editorguts.dll" at some point. Although later I think I was playing Shao-Lin's Road on the cocktail cabinet in the office and was amused by the protagonist saying "GUTS!" at the end of each level while flexing. I also enjoyed the Nickelodeon show and dream of owning a piece of the Aggro Crag. I mostly wanted to differentiate the new version from the last and I like the mental image of being elbows-deep in the guts of the game when you use the editor. Also, my Mom tells me Grandma wouldn't let her say "guts" as a kid, which I've always found amusing.Tell us about the NetherRealm tileset - what's the inspiration? Well, we had a very small taste of it in Torchlight II, and certainly hints of what that realm might look like, but we never crossed over, so to speak. So, the main idea was to go "into the portal" and visit the NetherRealm. We wanted it to feel as organic as possible and as dissimilar as we could make it to the other tilesets. Everything is built on a grid, and in some tilesets it's very apparent (as much as we tried to disguise it). This tileset had to look chaotic, organic, and make you forget about the grid. Along with that, we really wanted it to look barren, harsh, and completely alien.